The present invention relates to a solution concentration measuring method and a solution concentration measuring apparatus for measuring the concentration of a solute, for example, an optically active substance such as a protein dissolved in a sample solution.
More specifically, the present invention relates to a method and an apparatus for mixing a reagent in a sample solution to change the optical characteristics attributed to a specific component contained in the sample solution, and thereby measuring the concentration of the specific component.
As a solution concentration measuring method adopted in the prior art, there is a coloration method in which a reagent solution containing, for example, a metal ion, a coloring matter or an enzyme is mixed in a sample solution, and allowed to react with a specific component in the sample solution, whereby light absorption characteristic (light absorption spectrum) of the sample solution is changed and the change in the light absorption characteristic is measured by means of a spectroscope or the like.
Further, there is another method in which an acidic reagent solution containing a sulfosalicylic acid or the like is mixed in a sample solution to coagulate the protein in the sample solution, whereby the sample solution is made turbid to measure the turbidity.
Furthermore, there is a still other method in which to an antigen-containing sample solution, a reagent solution containing an antibody against the antigen is mixed to form an antigen-antibody complex, whereby the sample solution is made turbid to detect the reduction in the intensity of a light transmitted through the sample solution, and the increase in the intensity of a scattered light arisen when a light is propagated through the inside of the sample solution, thereby to determine the antigen concentration.
In this case, examples of the antigen when the sample solution is a urine include hemoglobin, albumin, luteinizing hormone and the like. Examples of the antigen when the sample solution is a blood include hemoglobin, saccharified protein, C-reactive protein (CRP) and the like.
On the other hand, as a solution concentration measuring apparatus adopted in the prior art, there is the one using a spectroscope, a liquid chromatograph, or the like. Further, as a urinalysis apparatus, there is a test paper impregnated with a reagent or the like. It is possible to examine a component of a urine by dipping the test paper in the urine, and observing the color reaction thereof by means of a spectroscope or the like. The test papers used herein are individually prepared according to respective inspection items such as glucose and protein.
However, in any of the methods and apparatuses described above, no particular measures have been taken to examine the change in the characteristics of the reagent to be used, and judge the precision of the solution concentration measurement with ease. The reason for this is that the necessity of considering the change in the characteristics of the reagent solution is low in the place where the control system with respect to the expiration date and the storage environment of the reagent solution is established, like a specialized facility such as a hospital.
Further, the person in charge having a technical skill in such a facility carries out the configuration and the functional test of the overall measuring system including a measuring device (spectroscope or the like), if required, by using a standard sample with a known concentration of a specific component (a control urine, a control blood serum, or the like). Therefore, such a countermeasure technology against the change in the characteristics of the reagent that even a layperson not trained can carry out has not been particularly required. Thus, sufficient development thereof has not been done.
However, when a solution concentration measurement examination is carried out at home or the like, there is the following problem. Namely, since there is a wide range of variation in the storage environment comprising temperature, humidity, and sunshine at home, the change in the characteristics of the reagent tends to exhibit a wide range of variation even within a certain period of storage. Particularly, the change in the characteristics of the reagent may exhibit a wide range of variation after opening a container containing the reagent.
Further, those in the ordinary households are not familiar with, and are not trained for the solution concentration measuring method to be applied to the urinalysis or the like. Therefore, the operation of the countermeasure technology against the change in the characteristics of the reagent is desirably as simple as possible, and automated.
Still further, in order for the solution concentration measuring apparatus as described above to come into wide use as a urinalysis apparatus at ordinary households, the apparatus is required to be reduced in size and cost.
In view of the foregoing problems, it is therefore an object of the present invention to provide a solution concentration measuring method whereby the reliability of the measurement is improved by examining the change in the characteristics of a reagent and judging the precision of the measurement, and a solution concentration measuring apparatus, which is compact in size and ensures ease of maintenance and control, usable for such a method.
In other words, it is an object of the present invention to judge the precision of the measurement using a reagent solution by examining the change in the characteristics of the reagent solution when the characteristics of the reagent solution change with time according to the storage environment. Specifically, it is an object of the present invention to provide a method whereby a measurement using a reagent solution is judged as being effective when the change in the characteristics (difference and/or ratio) departs from a predetermined range.
The present invention pertains to a solution concentration measuring method for measuring an optical characteristic of a mixed solution of a sample solution and a reagent solution, and thereby measuring the concentration of a specific component in the sample solution, which comprises the steps of: (1) previously determining a time-varying property A of the optical characteristic of the reagent solution at a time point of storage under a specific storage environment; (2) measuring an optical characteristic of a mixed solution of the sample solution and the reagent solution at the time point of storage to determine a time-varying property B of the optical characteristic of the mixed solution; and (3) judging the precision of a measured value of the concentration of the specific component based on the time-varying properties A and B.
It is effective that the step (3) is a step of forming a characteristic curve showing changes in the optical characteristic of the mixed solution with respect to changes in the optical characteristic of the reagent solution based on the time-varying properties A and B, examining a characteristic of the reagent solution based on the characteristic curve and a measured value obtained by measuring the optical characteristic of the reagent solution, and thereby judging the precision of a measured value of the concentration of the specific component.
It is effective that the optical characteristic of the mixed solution to be measured is an absorbance or a turbidity.
It is effective that the optical characteristic of the reagent solution to be measured is an absorbance or a turbidity.
It is effective that the optical characteristics of the mixed solution and the reagent solution to be measured are the same, and measured by using a light having the same wavelength.
It is effective that the optical characteristics of the mixed solution and the reagent solution to be measured are the same, and measured by means of the same optical characteristic measuring apparatus.
It is effective that the precision of a measured value of the concentration of the specific component is judged to be low when the turbidity of the reagent solution is high or low, and the precision of a measured value of the concentration of the specific component is judged to be high when the turbidity of the reagent solution is low or high.
It is effective that the precision of a measured value of the concentration of the specific component is judged to be high and effective when the turbidity of the reagent solution is not more than or not less than a predetermined value.
It is effective that the precision of a measured value of the concentration of the specific component is judged by taking an absorbance and/or a turbidity of the reagent solution to be used in a first round of the solution concentration measuring method immediately after manufacturing thereof as an initial value, and comparing an absorbance and/or a turbidity of the reagent solution to be used in a second or later round of the solution concentration measuring method is compared with the initial value.
It is effective that the measured value of the concentration of the specific component is judged to be effective when the difference and/or the ratio between the absorbance and/or the turbidity in the second or later round and the initial value is not more than a predetermined value.
The present invention also pertains to a solution concentration measuring apparatus, which comprises: a light source for irradiating a sample solution containing a specific component with a light; a sample cell for holding the sample solution such that a light transmits through the sample solution; a photosensor 1 for detecting the light transmitted through the sample solution and/or a photosensor 2 disposed so as to detect a scattered light arisen when the light propagates through the inside of the sample solution; a transfusion system for introducing the sample solution and a reagent solution into the sample cell; and a computer for controlling the transfusion system to analyze an output signal from the photosensor 1 and/or the photosensor 2, wherein the computer comprises: a memory unit for storing a time-varying property A of an optical characteristic of the reagent solution previously determined a time point of storage under a specific storage environment; a control unit for using an output signal from the photosensor 1 and/or the photosensor 2 as a measured value corresponding to an optical characteristic, and measuring an optical characteristic of a mixed solution of the sample solution and the reagent solution at the time point of storage to determine a time-varying property B of an optical characteristic of the mixed solution; a comparison unit for judging the precision of a measured value of the concentration of the specific component based on the time-varying properties A and B; and a display unit for displaying a result of the precision judgment.
It is effective that the control unit calculates the concentration of the specific component of the sample solution by using an output signal from the photosensor 2 as a measured value corresponding to the optical characteristic when the concentration of the sample solution with a low concentration of the specific component is determined, and using an output signal from the photosensor 1 as a measured value corresponding to the optical characteristic when the concentration of the sample solution with a high concentration of the specific component is determined, thereby to enlarge a measurable concentration range.
Further, it is effective that the control unit improves a characteristic examination precision of the reagent solution by using an output signal from the photosensor 2 as a measured value corresponding to the optical characteristic of the reagent solution.
While the novel features of the invention are set forth particularly in the appended claims, the invention, both as to organization and content, will be better understood and appreciated, along with other objects and features thereof, from the following detailed description taken in conjunction with the drawings.